This invention concerns a container closure having threads which are configured to allow for a great variation in the mating thread.
Molded plastic containers are in extremely wide use today, with many of the containers having an externally threaded neck which is adapted to mate with the internal threads of a container closure. It has been found that substantial variations exist in the parameters of the external threads of blow-molded containers. On some occasions, the expansion of the neck may have been larger than desired and the threads have a particular pitch and configuration while in other instances the expansion of the neck may be smaller than desired and the external threads have a significantly different pitch and configuration from the previously described threads.
When the container closure, which may have been injection molded, is attempted to be threaded onto the neck of the container, the substantial variation in the container neck thread parameters sometimes results in the inability of the closure to be threaded onto a container neck. An excessive tightness between the closure and the container may occur if the container neck is too large. An excessive looseness may occur between the closure and the container neck, particularly if the container neck is too small, thereby resulting in shifting of the closure with respect to the container neck. If the closure is too tight with respect to the container, the operator may experience difficulty in turning the closure and particles may be generated. On the other hand, if the closure is too loose with respect to the container, the closure may fall off and/or leakage may result.
In order for the neck of the container to have precise dimensions, an unusually expensive operation would be required. Such an expensive operation is not always feasible and yet it is desirable to have a properly mating container closure and container.
It is, therefore, an object of the present invention to provide an internally threaded closure for an externally threaded container, with the closure having a thread configuration that compensates for significant variations in the mating thread.
Another object of the present invention is to provide a container closure having compensating threads and having a configuration that is efficient to manufacture.
Other objects and advantages of the present invention will become apparent as the description proceeds.